This invention relates to a sterilizable, disposable lens housing and associated lens cover for the objective lens ring of an operating microscope and, in particular, to an improved structure of the housing and lens cover carried by the housing.
For many types of operations which involve the use of microsurgical techniques, an operating room microscope is used so that the physician can easily observe all of the elements in the surgical field. In order to maintain the sterility of all of the elements within the surgical field, disposable sterilized drapes are used for covering the microscope.
In order to prevent any distortion of images observed by the operating physician, optically clear lens covers have been developed for connection to the removable drape prior to the operation. Because certain types of surgical operations result in bone fragments and/or blood being splattered on the lens cover, it is important to have a lens cover and housing where the lens cover can easily be removed and replaced, if desired, so that the surgeon can have a clear and unobstructed view of the surgical field.
One lens housing and cover generally of the type described is the subject of U.S. Pat. No. 3,796,477 where a housing formed of a flexible, easily distortable resilient material such as 70 durometer PVC is described. In that patent, an annular housing with a groove along its entire inner surface is designed to receive a lens cover which fits within the groove. The cover has a tab portion designed to fit within a slot formed in the outer surface of the ring. Although this ring has been used over the years, it has the disadvantage of having a lens cover that is somewhat difficult to insert into the annular ring because the cover must be inserted with the leading edge first placed in the groove and then the tab pushed down into the slot.
Another type of lens housing is shown in U.S. Pat. No. 4,564,270 where a housing with a laminated structure is provided to be used with a lens cover that is slidable into a U-shaped slot formed between two adjacent portions. The slot is generally equal in size to the lens cover which is inserted. The perimeter of the lens is formed with a roughened surface which is said to maintain the lens cover within the slot of the housing which is not considered to be a sufficient way for holding the lens in the slot. Furthermore, since the thickness of the slot within which the lens cover is inserted is equal to the width of the cover, so that if blood or other debris is splattered on the cover and the cover is removed the debris will be deposited and spread along the adjacent surface. This either results in an accumulation of the debris or causes the debris to be redeposited on a replacement lens cover if one is re-inserted into the holder.